The present invention relates to a manufacturing method of a semiconductor device, and in particular, to a technique effective when applied to a dry etching step in which light emitted from a processing chamber is detected, and the end point of etching is detected based on a change in its emission intensity.
In semiconductor manufacturing processes, a technique is widely used, in which the end point of a process is detected by monitoring changes in plasma emission in a process chamber. Also, in dry etching steps, a light emission monitoring method is adopted as an etching end point detection method in most equipment, in which the end point of etching is detected by monitoring changes in the emission intensity of an etching gas component that emits light in plasma or in the emission intensity of a reaction product generated in plasma.
On the other hand, the area of a portion to be etched is being reduced with the miniaturization of semiconductor products, and in particular, in via hole etching for forming a via hole (contact hole) in an interlayer insulating film, such as a silicon oxide film, it becomes difficult to accurately detect an end point because of a reduction in the opening area of a via hole.
For example, in via hole etching, when it is determined that the end point of etching has been reached in the middle of the etching of an interlayer insulating, the via hole does not reach an underlying metal wiring layer, whereby a conduction defect is caused in the via. On the contrary, when a via hole reaches a metal wiring main body (aluminum film) by penetrating a barrier metal for an underlying metal wiring layer, a high-resistance layer, such as aluminum fluoride, is formed by reacting with a fluorine component contained in etching gas, which leads to a high-resistance defect in the via. To deal with these problems, various methods for increasing the accuracy of end point detection, such as monitoring in combination of emission of two wavelengths, are being considered.
For example, the technique as disclosed in Patent Document 1 is cited as a background technique of the present technical field. Patent Document 1 discloses a “technique for improving the reliability of a semiconductor device, in which a disconnection defect in the bottom of a via is prevented by prohibiting wiring having a large volume from being arranged below the via.”
Additionally, Patent Document 2 discloses a “technique for stably detecting the end point of etching, in which the end point of etching is detected at a second inflection point by performing a secondary differential operation on the time series data of an emission intensity ratio between two light beams each having a wavelength.”